Energy saving startup circuit for power supply
a startup circuit and power supply technology, applied in the direction of electric variable regulation, process and machine control, instruments, etc., can solve the problems of reducing the overall reducing the efficiency of the power supply, and difficulty in optimizing, so as to prevent energy loss and improve efficiency.
Active Publication Date: 2007-05-10
LIGHTECH ELECTRONICS INDS
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- Abstract
- Description
- Claims
- Application Information
AI Technical Summary
Benefits of technology
[0011] It is therefore an object of the invention to provide a startup circuit for a power supply having near unity power factor, having a starting resistor that is disconnected after the power supply has reached steady state, thereby preventing energy loss and improving efficiency.
Problems solved by technology
However, once the power supply is operating and has reached a steady state voltage, there is no longer any need to supply energy to the starting circuit, which is now redundant.
A drawback with the arrangement shown in FIG. 1 is that even under steady state conditions, when the starting circuit is no longer necessary, the constant flow of current through the starting resistor 4 manifests itself as a constant energy loss, thus reducing the overall efficiency of the power supply.
However, in so-called universal power supplies that are intended to operate over a range of power supply voltages, such as 85-277 VAC so as to be suitable for both the US and European markets, such optimization is difficult to achieve and it becomes impossible to minimize the energy loss through the starting resistor for all supply voltages.
However, the connection of a high capacitance at the input of the circuit militates against the power supply having near unity power factor.
However, there are many applications where near unity power factor is required and, in such cases, the circuit shown in JP 2001275347 is unsuitable.
This increases the time that it takes for steady state to be reached and this in turn increases the time before the startup circuit must be disabled.
Method used
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Embodiment Construction
[0023]FIG. 3 is a block diagram showing functionally an improved startup circuit according to the invention having an input 31 for connecting thereto a mains supply voltage (constituting a source of high voltage). Typically, such supply has a voltage of 110 VAC in the USA or 220 VAC in Europe. The input 31 is connected to a bridge rectifier 32 having an output 33 that feeds rectified voltage to a current source 34 that is coupled to one end of a capacitor 35 (constituting a first energy storage device) whose other end is connected to GND.
[0024] A normally open switching circuit 36 is coupled to the first capacitor and to a second capacitor 37 (constituting a second energy storage device) and is responsive to the output of a first comparator 38 having a first input 39 connected to the positive voltage terminal of the first capacitor 35 and having a second input 40 connected to a first reference voltage (VR1). The current source 34 is responsively coupled to the output of a second co...
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A startup circuit (30) for a power supply (44), has an input (31) for connecting to a source of high voltage thereo, and an output rail (33) for feeding rectified voltage to the power supply. A first energy storage device (35) is coupled to the output rail for storing energy when voltage is first applied to the input, and a second energy storage device (37) is coupled to an output of the power supply for storing energy when a voltage appearing at the output of the power supply reaches substantially steady state. A switching circuit (36, 50) is coupled to the first energy storage device and the second energy storage device and is responsive to the first energy storage device having sufficient energy for transferring the energy to the second energy storage device and disconnecting the first energy storage device from the output rail.
Description
FIELD OF THE INVENTION [0001] This invention relates to startup circuits for driving low voltage equipment such as light emitting diodes (LEDs). BACKGROUND OF THE INVENTION [0002] Electrical equipment requiring low voltage DC are frequently energized by mains operated power supplies. FIG. 1 shows schematically a conventional startup circuit 1 in a typical low voltage power supply, wherein mains voltage 2 is rectified typically by a bridge rectifier 3 and then fed via a resistor 4 to a control circuit (not shown) in the power supply. The input voltage to the control circuit is maintained at a required level by a zener diode 5 connected in parallel with a capacitor 6. [0003] During operation, the resistor 4, which will be referred throughout as a “starting resistor”, feeds current to the capacitor 6 which therefore charges to a value determined by the zener diode 5, thus ensuring a constant voltage input to the control circuit. Typically, the mains voltage is 110 VAC in the USA or 220...
Claims
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Patent Timeline
Login to View More IPC IPC(8): H02M1/00H02M1/12H02M3/335H05B44/00
CPCH02M1/12H02M3/335H05B33/0806H05B45/355
InventorPATCHORNIK, JOSHUA
OwnerLIGHTECH ELECTRONICS INDS